Oxford Instruments NanoScience MercuryiPS - Heater Resistance (Htr Res); Switch Resistance (Sw Res); Lead Resistance (Lead)

Operator's Manual
Issue 14 / Mar 2016
/ UMC0071
MercuryiPS
©2016 Oxford Instruments NanoScience. All rights reserved.
Page 51
This value can be defined from the state of the switch when the switch is in its
superconducting state and the second term of the above equation is zero. In this case
RIP
SwHtrSwHtrlSwitchTota
*
2
0

where I
SwHtr0
is the switch heater current required to keep the switch in the normal state
when the magnet current is zero (i.e. I
op
= 0 and V
op
= 0). This is defined in the
configuration table for non-intelligent switch operation (section 4.4.8). So, in intelligent
switch mode the switch heater current is calculated as
 


RR
RI
V
II
SwHtrSwitch
leadsopop
SwHtrSwHtr
*
*
2
2
0


Therefore the iPS system adjusts the switch heater current based on the variation of the
voltage across the switch (V
op
– I
op
*R
leads
) to keep P
SwitchTotal
constant.
When the switch heater is switched OFF the switch heater current reverts to its 0mA
value.
4.4.14 Htr Res ()
Parameter used as above. This value is an estimate of the switch heater resistance.
4.4.15 Sw Res ()
Parameter used as above. This value is an estimate of the switch superconducting element
resistance when it’s in its “normal” (non-superconducting) state.
4.4.16 Lead ()
Parameter used as above. This value is an estimate of the main current leads total resistance.
The power supply can also calculate this value and may update this value in its normal
operating cycle.